[GFS2] Tidy up meta_io code

[mirror_ubuntu-artful-kernel.git] / fs / gfs2 / bmap.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/gfs2_ondisk.h>
#include <linux/crc32.h>
#include <linux/lm_interface.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "glock.h"
#include "inode.h"
#include "meta_io.h"
#include "quota.h"
#include "rgrp.h"
#include "trans.h"
#include "dir.h"
#include "util.h"
#include "ops_address.h"

/* This doesn't need to be that large as max 64 bit pointers in a 4k
 * block is 512, so __u16 is fine for that. It saves stack space to
 * keep it small.
 */
struct metapath {
        __u16 mp_list[GFS2_MAX_META_HEIGHT];
};

typedef int (*block_call_t) (struct gfs2_inode *ip, struct buffer_head *dibh,
                             struct buffer_head *bh, u64 *top,
                             u64 *bottom, unsigned int height,
                             void *data);

struct strip_mine {
        int sm_first;
        unsigned int sm_height;
};

/**
 * gfs2_unstuffer_page - unstuff a stuffed inode into a block cached by a page
 * @ip: the inode
 * @dibh: the dinode buffer
 * @block: the block number that was allocated
 * @private: any locked page held by the caller process
 *
 * Returns: errno
 */

static int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
                               u64 block, struct page *page)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct inode *inode = &ip->i_inode;
        struct buffer_head *bh;
        int release = 0;

        if (!page || page->index) {
                page = grab_cache_page(inode->i_mapping, 0);
                if (!page)
                        return -ENOMEM;
                release = 1;
        }

        if (!PageUptodate(page)) {
                void *kaddr = kmap(page);

                memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode),
                       ip->i_di.di_size);
                memset(kaddr + ip->i_di.di_size, 0,
                       PAGE_CACHE_SIZE - ip->i_di.di_size);
                kunmap(page);

                SetPageUptodate(page);
        }

        if (!page_has_buffers(page))
                create_empty_buffers(page, 1 << inode->i_blkbits,
                                     (1 << BH_Uptodate));

        bh = page_buffers(page);

        if (!buffer_mapped(bh))
                map_bh(bh, inode->i_sb, block);

        set_buffer_uptodate(bh);
        if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
                gfs2_trans_add_bh(ip->i_gl, bh, 0);
        mark_buffer_dirty(bh);

        if (release) {
                unlock_page(page);
                page_cache_release(page);
        }

        return 0;
}

/**
 * gfs2_unstuff_dinode - Unstuff a dinode when the data has grown too big
 * @ip: The GFS2 inode to unstuff
 * @unstuffer: the routine that handles unstuffing a non-zero length file
 * @private: private data for the unstuffer
 *
 * This routine unstuffs a dinode and returns it to a "normal" state such
 * that the height can be grown in the traditional way.
 *
 * Returns: errno
 */

int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page)
{
        struct buffer_head *bh, *dibh;
        u64 block = 0;
        int isdir = gfs2_is_dir(ip);
        int error;

        down_write(&ip->i_rw_mutex);

        error = gfs2_meta_inode_buffer(ip, &dibh);
        if (error)
                goto out;
                
        if (ip->i_di.di_size) {
                /* Get a free block, fill it with the stuffed data,
                   and write it out to disk */

                if (isdir) {
                        block = gfs2_alloc_meta(ip);

                        error = gfs2_dir_get_new_buffer(ip, block, &bh);
                        if (error)
                                goto out_brelse;
                        gfs2_buffer_copy_tail(bh,
                                              sizeof(struct gfs2_meta_header),
                                              dibh, sizeof(struct gfs2_dinode));
                        brelse(bh);
                } else {
                        block = gfs2_alloc_data(ip);

                        error = gfs2_unstuffer_page(ip, dibh, block, page);
                        if (error)
                                goto out_brelse;
                }
        }

        /*  Set up the pointer to the new block  */

        gfs2_trans_add_bh(ip->i_gl, dibh, 1);

        gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));

        if (ip->i_di.di_size) {
                *(u64 *)(dibh->b_data + sizeof(struct gfs2_dinode)) =
                        cpu_to_be64(block);
                ip->i_di.di_blocks++;
        }

        ip->i_di.di_height = 1;

        gfs2_dinode_out(&ip->i_di, dibh->b_data);

out_brelse:
        brelse(dibh);
out:
        up_write(&ip->i_rw_mutex);
        return error;
}

/**
 * calc_tree_height - Calculate the height of a metadata tree
 * @ip: The GFS2 inode
 * @size: The proposed size of the file
 *
 * Work out how tall a metadata tree needs to be in order to accommodate a
 * file of a particular size. If size is less than the current size of
 * the inode, then the current size of the inode is used instead of the
 * supplied one.
 *
 * Returns: the height the tree should be
 */

static unsigned int calc_tree_height(struct gfs2_inode *ip, u64 size)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        u64 *arr;
        unsigned int max, height;

        if (ip->i_di.di_size > size)
                size = ip->i_di.di_size;

        if (gfs2_is_dir(ip)) {
                arr = sdp->sd_jheightsize;
                max = sdp->sd_max_jheight;
        } else {
                arr = sdp->sd_heightsize;
                max = sdp->sd_max_height;
        }

        for (height = 0; height < max; height++)
                if (arr[height] >= size)
                        break;

        return height;
}

/**
 * build_height - Build a metadata tree of the requested height
 * @ip: The GFS2 inode
 * @height: The height to build to
 *
 *
 * Returns: errno
 */

static int build_height(struct inode *inode, unsigned height)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        unsigned new_height = height - ip->i_di.di_height;
        struct buffer_head *dibh;
        struct buffer_head *blocks[GFS2_MAX_META_HEIGHT];
        int error;
        u64 *bp;
        u64 bn;
        unsigned n;

        if (height <= ip->i_di.di_height)
                return 0;

        error = gfs2_meta_inode_buffer(ip, &dibh);
        if (error)
                return error;

        for(n = 0; n < new_height; n++) {
                bn = gfs2_alloc_meta(ip);
                blocks[n] = gfs2_meta_new(ip->i_gl, bn);
                gfs2_trans_add_bh(ip->i_gl, blocks[n], 1);
        }
        
        n = 0;
        bn = blocks[0]->b_blocknr;
        if (new_height > 1) {
                for(; n < new_height-1; n++) {
                        gfs2_metatype_set(blocks[n], GFS2_METATYPE_IN,
                                          GFS2_FORMAT_IN);
                        gfs2_buffer_clear_tail(blocks[n],
                                               sizeof(struct gfs2_meta_header));
                        bp = (u64 *)(blocks[n]->b_data +
                                     sizeof(struct gfs2_meta_header));
                        *bp = cpu_to_be64(blocks[n+1]->b_blocknr);
                        brelse(blocks[n]);
                        blocks[n] = NULL;
                }
        }
        gfs2_metatype_set(blocks[n], GFS2_METATYPE_IN, GFS2_FORMAT_IN);
        gfs2_buffer_copy_tail(blocks[n], sizeof(struct gfs2_meta_header),
                              dibh, sizeof(struct gfs2_dinode));
        brelse(blocks[n]);
        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
        gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
        bp = (u64 *)(dibh->b_data + sizeof(struct gfs2_dinode));
        *bp = cpu_to_be64(bn);
        ip->i_di.di_height += new_height;
        ip->i_di.di_blocks += new_height;
        gfs2_dinode_out(&ip->i_di, dibh->b_data);
        brelse(dibh);
        return error;
}

/**
 * find_metapath - Find path through the metadata tree
 * @ip: The inode pointer
 * @mp: The metapath to return the result in
 * @block: The disk block to look up
 *
 *   This routine returns a struct metapath structure that defines a path
 *   through the metadata of inode "ip" to get to block "block".
 *
 *   Example:
 *   Given:  "ip" is a height 3 file, "offset" is 101342453, and this is a
 *   filesystem with a blocksize of 4096.
 *
 *   find_metapath() would return a struct metapath structure set to:
 *   mp_offset = 101342453, mp_height = 3, mp_list[0] = 0, mp_list[1] = 48,
 *   and mp_list[2] = 165.
 *
 *   That means that in order to get to the block containing the byte at
 *   offset 101342453, we would load the indirect block pointed to by pointer
 *   0 in the dinode.  We would then load the indirect block pointed to by
 *   pointer 48 in that indirect block.  We would then load the data block
 *   pointed to by pointer 165 in that indirect block.
 *
 *             ----------------------------------------
 *             | Dinode |                             |
 *             |        |                            4|
 *             |        |0 1 2 3 4 5                 9|
 *             |        |                            6|
 *             ----------------------------------------
 *                       |
 *                       |
 *                       V
 *             ----------------------------------------
 *             | Indirect Block                       |
 *             |                                     5|
 *             |            4 4 4 4 4 5 5            1|
 *             |0           5 6 7 8 9 0 1            2|
 *             ----------------------------------------
 *                                |
 *                                |
 *                                V
 *             ----------------------------------------
 *             | Indirect Block                       |
 *             |                         1 1 1 1 1   5|
 *             |                         6 6 6 6 6   1|
 *             |0                        3 4 5 6 7   2|
 *             ----------------------------------------
 *                                           |
 *                                           |
 *                                           V
 *             ----------------------------------------
 *             | Data block containing offset         |
 *             |            101342453                 |
 *             |                                      |
 *             |                                      |
 *             ----------------------------------------
 *
 */

static void find_metapath(struct gfs2_inode *ip, u64 block,
                          struct metapath *mp)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        u64 b = block;
        unsigned int i;

        for (i = ip->i_di.di_height; i--;)
                mp->mp_list[i] = do_div(b, sdp->sd_inptrs);

}

/**
 * metapointer - Return pointer to start of metadata in a buffer
 * @bh: The buffer
 * @height: The metadata height (0 = dinode)
 * @mp: The metapath
 *
 * Return a pointer to the block number of the next height of the metadata
 * tree given a buffer containing the pointer to the current height of the
 * metadata tree.
 */

static inline u64 *metapointer(struct buffer_head *bh, int *boundary,
                               unsigned int height, const struct metapath *mp)
{
        unsigned int head_size = (height > 0) ?
                sizeof(struct gfs2_meta_header) : sizeof(struct gfs2_dinode);
        u64 *ptr;
        *boundary = 0;
        ptr = ((u64 *)(bh->b_data + head_size)) + mp->mp_list[height];
        if (ptr + 1 == (u64 *)(bh->b_data + bh->b_size))
                *boundary = 1;
        return ptr;
}

/**
 * lookup_block - Get the next metadata block in metadata tree
 * @ip: The GFS2 inode
 * @bh: Buffer containing the pointers to metadata blocks
 * @height: The height of the tree (0 = dinode)
 * @mp: The metapath
 * @create: Non-zero if we may create a new meatdata block
 * @new: Used to indicate if we did create a new metadata block
 * @block: the returned disk block number
 *
 * Given a metatree, complete to a particular height, checks to see if the next
 * height of the tree exists. If not the next height of the tree is created.
 * The block number of the next height of the metadata tree is returned.
 *
 */

static int lookup_block(struct gfs2_inode *ip, struct buffer_head *bh,
                        unsigned int height, struct metapath *mp, int create,
                        int *new, u64 *block)
{
        int boundary;
        u64 *ptr = metapointer(bh, &boundary, height, mp);

        if (*ptr) {
                *block = be64_to_cpu(*ptr);
                return boundary;
        }

        *block = 0;

        if (!create)
                return 0;

        if (height == ip->i_di.di_height - 1 && !gfs2_is_dir(ip))
                *block = gfs2_alloc_data(ip);
        else
                *block = gfs2_alloc_meta(ip);

        gfs2_trans_add_bh(ip->i_gl, bh, 1);

        *ptr = cpu_to_be64(*block);
        ip->i_di.di_blocks++;

        *new = 1;
        return 0;
}

/**
 * gfs2_block_pointers - Map a block from an inode to a disk block
 * @inode: The inode
 * @lblock: The logical block number
 * @map_bh: The bh to be mapped
 * @mp: metapath to use
 *
 * Find the block number on the current device which corresponds to an
 * inode's block. If the block had to be created, "new" will be set.
 *
 * Returns: errno
 */

static int gfs2_block_pointers(struct inode *inode, u64 lblock, int create,
                               struct buffer_head *bh_map, struct metapath *mp,
                               unsigned int maxlen)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct buffer_head *bh;
        unsigned int bsize;
        unsigned int height;
        unsigned int end_of_metadata;
        unsigned int x;
        int error = 0;
        int new = 0;
        u64 dblock = 0;
        int boundary;

        BUG_ON(maxlen == 0);

        if (gfs2_assert_warn(sdp, !gfs2_is_stuffed(ip)))
                return 0;

        bsize = gfs2_is_dir(ip) ? sdp->sd_jbsize : sdp->sd_sb.sb_bsize;

        height = calc_tree_height(ip, (lblock + 1) * bsize);
        if (ip->i_di.di_height < height) {
                if (!create)
                        return 0;

                error = build_height(inode, height);
                if (error)
                        return error;
        }

        find_metapath(ip, lblock, mp);
        end_of_metadata = ip->i_di.di_height - 1;

        error = gfs2_meta_inode_buffer(ip, &bh);
        if (error)
                return error;

        for (x = 0; x < end_of_metadata; x++) {
                lookup_block(ip, bh, x, mp, create, &new, &dblock);
                brelse(bh);
                if (!dblock)
                        return 0;

                error = gfs2_meta_indirect_buffer(ip, x+1, dblock, new, &bh);
                if (error)
                        return error;
        }

        boundary = lookup_block(ip, bh, end_of_metadata, mp, create, &new, &dblock);
        clear_buffer_mapped(bh_map);
        clear_buffer_new(bh_map);
        clear_buffer_boundary(bh_map);

        if (dblock) {
                map_bh(bh_map, inode->i_sb, dblock);
                if (boundary)
                        set_buffer_boundary(bh);
                if (new) {
                        struct buffer_head *dibh;
                        error = gfs2_meta_inode_buffer(ip, &dibh);
                        if (!error) {
                                gfs2_trans_add_bh(ip->i_gl, dibh, 1);
                                gfs2_dinode_out(&ip->i_di, dibh->b_data);
                                brelse(dibh);
                        }
                        set_buffer_new(bh_map);
                        goto out_brelse;
                }
                while(--maxlen && !buffer_boundary(bh_map)) {
                        u64 eblock;

                        mp->mp_list[end_of_metadata]++;
                        boundary = lookup_block(ip, bh, end_of_metadata, mp, 0, &new, &eblock);
                        if (eblock != ++dblock)
                                break;
                        bh_map->b_size += (1 << inode->i_blkbits);
                        if (boundary)
                                set_buffer_boundary(bh_map);
                }
        }
out_brelse:
        brelse(bh);
        return 0;
}


static inline void bmap_lock(struct inode *inode, int create)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        if (create)
                down_write(&ip->i_rw_mutex);
        else
                down_read(&ip->i_rw_mutex);
}

static inline void bmap_unlock(struct inode *inode, int create)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        if (create)
                up_write(&ip->i_rw_mutex);
        else
                up_read(&ip->i_rw_mutex);
}

int gfs2_block_map(struct inode *inode, u64 lblock, int create,
                   struct buffer_head *bh, unsigned int maxlen)
{
        struct metapath mp;
        int ret;

        bmap_lock(inode, create);
        ret = gfs2_block_pointers(inode, lblock, create, bh, &mp, maxlen);
        bmap_unlock(inode, create);
        return ret;
}

int gfs2_extent_map(struct inode *inode, u64 lblock, int *new, u64 *dblock, unsigned *extlen)
{
        struct metapath mp;
        struct buffer_head bh = { .b_state = 0, .b_blocknr = 0, .b_size = 0 };
        int ret;
        int create = *new;

        BUG_ON(!extlen);
        BUG_ON(!dblock);
        BUG_ON(!new);

        bmap_lock(inode, create);
        ret = gfs2_block_pointers(inode, lblock, create, &bh, &mp, 32);
        bmap_unlock(inode, create);
        *extlen = bh.b_size >> inode->i_blkbits;
        *dblock = bh.b_blocknr;
        if (buffer_new(&bh))
                *new = 1;
        else
                *new = 0;
        return ret;
}

/**
 * recursive_scan - recursively scan through the end of a file
 * @ip: the inode
 * @dibh: the dinode buffer
 * @mp: the path through the metadata to the point to start
 * @height: the height the recursion is at
 * @block: the indirect block to look at
 * @first: 1 if this is the first block
 * @bc: the call to make for each piece of metadata
 * @data: data opaque to this function to pass to @bc
 *
 * When this is first called @height and @block should be zero and
 * @first should be 1.
 *
 * Returns: errno
 */

static int recursive_scan(struct gfs2_inode *ip, struct buffer_head *dibh,
                          struct metapath *mp, unsigned int height,
                          u64 block, int first, block_call_t bc,
                          void *data)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct buffer_head *bh = NULL;
        u64 *top, *bottom;
        u64 bn;
        int error;
        int mh_size = sizeof(struct gfs2_meta_header);

        if (!height) {
                error = gfs2_meta_inode_buffer(ip, &bh);
                if (error)
                        return error;
                dibh = bh;

                top = (u64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + mp->mp_list[0];
                bottom = (u64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + sdp->sd_diptrs;
        } else {
                error = gfs2_meta_indirect_buffer(ip, height, block, 0, &bh);
                if (error)
                        return error;

                top = (u64 *)(bh->b_data + mh_size) +
                                  (first ? mp->mp_list[height] : 0);

                bottom = (u64 *)(bh->b_data + mh_size) + sdp->sd_inptrs;
        }

        error = bc(ip, dibh, bh, top, bottom, height, data);
        if (error)
                goto out;

        if (height < ip->i_di.di_height - 1)
                for (; top < bottom; top++, first = 0) {
                        if (!*top)
                                continue;

                        bn = be64_to_cpu(*top);

                        error = recursive_scan(ip, dibh, mp, height + 1, bn,
                                               first, bc, data);
                        if (error)
                                break;
                }

out:
        brelse(bh);
        return error;
}

/**
 * do_strip - Look for a layer a particular layer of the file and strip it off
 * @ip: the inode
 * @dibh: the dinode buffer
 * @bh: A buffer of pointers
 * @top: The first pointer in the buffer
 * @bottom: One more than the last pointer
 * @height: the height this buffer is at
 * @data: a pointer to a struct strip_mine
 *
 * Returns: errno
 */

static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
                    struct buffer_head *bh, u64 *top, u64 *bottom,
                    unsigned int height, void *data)
{
        struct strip_mine *sm = data;
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct gfs2_rgrp_list rlist;
        u64 bn, bstart;
        u32 blen;
        u64 *p;
        unsigned int rg_blocks = 0;
        int metadata;
        unsigned int revokes = 0;
        int x;
        int error;

        if (!*top)
                sm->sm_first = 0;

        if (height != sm->sm_height)
                return 0;

        if (sm->sm_first) {
                top++;
                sm->sm_first = 0;
        }

        metadata = (height != ip->i_di.di_height - 1);
        if (metadata)
                revokes = (height) ? sdp->sd_inptrs : sdp->sd_diptrs;

        error = gfs2_rindex_hold(sdp, &ip->i_alloc.al_ri_gh);
        if (error)
                return error;

        memset(&rlist, 0, sizeof(struct gfs2_rgrp_list));
        bstart = 0;
        blen = 0;

        for (p = top; p < bottom; p++) {
                if (!*p)
                        continue;

                bn = be64_to_cpu(*p);

                if (bstart + blen == bn)
                        blen++;
                else {
                        if (bstart)
                                gfs2_rlist_add(sdp, &rlist, bstart);

                        bstart = bn;
                        blen = 1;
                }
        }

        if (bstart)
                gfs2_rlist_add(sdp, &rlist, bstart);
        else
                goto out; /* Nothing to do */

        gfs2_rlist_alloc(&rlist, LM_ST_EXCLUSIVE, 0);

        for (x = 0; x < rlist.rl_rgrps; x++) {
                struct gfs2_rgrpd *rgd;
                rgd = rlist.rl_ghs[x].gh_gl->gl_object;
                rg_blocks += rgd->rd_ri.ri_length;
        }

        error = gfs2_glock_nq_m(rlist.rl_rgrps, rlist.rl_ghs);
        if (error)
                goto out_rlist;

        error = gfs2_trans_begin(sdp, rg_blocks + RES_DINODE +
                                 RES_INDIRECT + RES_STATFS + RES_QUOTA,
                                 revokes);
        if (error)
                goto out_rg_gunlock;

        down_write(&ip->i_rw_mutex);

        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
        gfs2_trans_add_bh(ip->i_gl, bh, 1);

        bstart = 0;
        blen = 0;

        for (p = top; p < bottom; p++) {
                if (!*p)
                        continue;

                bn = be64_to_cpu(*p);

                if (bstart + blen == bn)
                        blen++;
                else {
                        if (bstart) {
                                if (metadata)
                                        gfs2_free_meta(ip, bstart, blen);
                                else
                                        gfs2_free_data(ip, bstart, blen);
                        }

                        bstart = bn;
                        blen = 1;
                }

                *p = 0;
                if (!ip->i_di.di_blocks)
                        gfs2_consist_inode(ip);
                ip->i_di.di_blocks--;
        }
        if (bstart) {
                if (metadata)
                        gfs2_free_meta(ip, bstart, blen);
                else
                        gfs2_free_data(ip, bstart, blen);
        }

        ip->i_di.di_mtime = ip->i_di.di_ctime = get_seconds();

        gfs2_dinode_out(&ip->i_di, dibh->b_data);

        up_write(&ip->i_rw_mutex);

        gfs2_trans_end(sdp);

out_rg_gunlock:
        gfs2_glock_dq_m(rlist.rl_rgrps, rlist.rl_ghs);
out_rlist:
        gfs2_rlist_free(&rlist);
out:
        gfs2_glock_dq_uninit(&ip->i_alloc.al_ri_gh);
        return error;
}

/**
 * do_grow - Make a file look bigger than it is
 * @ip: the inode
 * @size: the size to set the file to
 *
 * Called with an exclusive lock on @ip.
 *
 * Returns: errno
 */

static int do_grow(struct gfs2_inode *ip, u64 size)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct gfs2_alloc *al;
        struct buffer_head *dibh;
        unsigned int h;
        int error;

        al = gfs2_alloc_get(ip);

        error = gfs2_quota_lock(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
        if (error)
                goto out;

        error = gfs2_quota_check(ip, ip->i_di.di_uid, ip->i_di.di_gid);
        if (error)
                goto out_gunlock_q;

        al->al_requested = sdp->sd_max_height + RES_DATA;

        error = gfs2_inplace_reserve(ip);
        if (error)
                goto out_gunlock_q;

        error = gfs2_trans_begin(sdp,
                        sdp->sd_max_height + al->al_rgd->rd_ri.ri_length +
                        RES_JDATA + RES_DINODE + RES_STATFS + RES_QUOTA, 0);
        if (error)
                goto out_ipres;

        if (size > sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)) {
                if (gfs2_is_stuffed(ip)) {
                        error = gfs2_unstuff_dinode(ip, NULL);
                        if (error)
                                goto out_end_trans;
                }

                h = calc_tree_height(ip, size);
                if (ip->i_di.di_height < h) {
                        down_write(&ip->i_rw_mutex);
                        error = build_height(&ip->i_inode, h);
                        up_write(&ip->i_rw_mutex);
                        if (error)
                                goto out_end_trans;
                }
        }

        ip->i_di.di_size = size;
        ip->i_di.di_mtime = ip->i_di.di_ctime = get_seconds();

        error = gfs2_meta_inode_buffer(ip, &dibh);
        if (error)
                goto out_end_trans;

        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
        gfs2_dinode_out(&ip->i_di, dibh->b_data);
        brelse(dibh);

out_end_trans:
        gfs2_trans_end(sdp);
out_ipres:
        gfs2_inplace_release(ip);
out_gunlock_q:
        gfs2_quota_unlock(ip);
out:
        gfs2_alloc_put(ip);
        return error;
}


/**
 * gfs2_block_truncate_page - Deal with zeroing out data for truncate
 *
 * This is partly borrowed from ext3.
 */
static int gfs2_block_truncate_page(struct address_space *mapping)
{
        struct inode *inode = mapping->host;
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        loff_t from = inode->i_size;
        unsigned long index = from >> PAGE_CACHE_SHIFT;
        unsigned offset = from & (PAGE_CACHE_SIZE-1);
        unsigned blocksize, iblock, length, pos;
        struct buffer_head *bh;
        struct page *page;
        void *kaddr;
        int err;

        page = grab_cache_page(mapping, index);
        if (!page)
                return 0;

        blocksize = inode->i_sb->s_blocksize;
        length = blocksize - (offset & (blocksize - 1));
        iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);

        if (!page_has_buffers(page))
                create_empty_buffers(page, blocksize, 0);

        /* Find the buffer that contains "offset" */
        bh = page_buffers(page);
        pos = blocksize;
        while (offset >= pos) {
                bh = bh->b_this_page;
                iblock++;
                pos += blocksize;
        }

        err = 0;

        if (!buffer_mapped(bh)) {
                gfs2_get_block(inode, iblock, bh, 0);
                /* unmapped? It's a hole - nothing to do */
                if (!buffer_mapped(bh))
                        goto unlock;
        }

        /* Ok, it's mapped. Make sure it's up-to-date */
        if (PageUptodate(page))
                set_buffer_uptodate(bh);

        if (!buffer_uptodate(bh)) {
                err = -EIO;
                ll_rw_block(READ, 1, &bh);
                wait_on_buffer(bh);
                /* Uhhuh. Read error. Complain and punt. */
                if (!buffer_uptodate(bh))
                        goto unlock;
        }

        if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
                gfs2_trans_add_bh(ip->i_gl, bh, 0);

        kaddr = kmap_atomic(page, KM_USER0);
        memset(kaddr + offset, 0, length);
        flush_dcache_page(page);
        kunmap_atomic(kaddr, KM_USER0);

unlock:
        unlock_page(page);
        page_cache_release(page);
        return err;
}

static int trunc_start(struct gfs2_inode *ip, u64 size)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct buffer_head *dibh;
        int journaled = gfs2_is_jdata(ip);
        int error;

        error = gfs2_trans_begin(sdp,
                                 RES_DINODE + (journaled ? RES_JDATA : 0), 0);
        if (error)
                return error;

        error = gfs2_meta_inode_buffer(ip, &dibh);
        if (error)
                goto out;

        if (gfs2_is_stuffed(ip)) {
                ip->i_di.di_size = size;
                ip->i_di.di_mtime = ip->i_di.di_ctime = get_seconds();
                gfs2_trans_add_bh(ip->i_gl, dibh, 1);
                gfs2_dinode_out(&ip->i_di, dibh->b_data);
                gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode) + size);
                error = 1;

        } else {
                if (size & (u64)(sdp->sd_sb.sb_bsize - 1))
                        error = gfs2_block_truncate_page(ip->i_inode.i_mapping);

                if (!error) {
                        ip->i_di.di_size = size;
                        ip->i_di.di_mtime = ip->i_di.di_ctime = get_seconds();
                        ip->i_di.di_flags |= GFS2_DIF_TRUNC_IN_PROG;
                        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
                        gfs2_dinode_out(&ip->i_di, dibh->b_data);
                }
        }

        brelse(dibh);

out:
        gfs2_trans_end(sdp);
        return error;
}

static int trunc_dealloc(struct gfs2_inode *ip, u64 size)
{
        unsigned int height = ip->i_di.di_height;
        u64 lblock;
        struct metapath mp;
        int error;

        if (!size)
                lblock = 0;
        else
                lblock = (size - 1) >> GFS2_SB(&ip->i_inode)->sd_sb.sb_bsize_shift;

        find_metapath(ip, lblock, &mp);
        gfs2_alloc_get(ip);

        error = gfs2_quota_hold(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
        if (error)
                goto out;

        while (height--) {
                struct strip_mine sm;
                sm.sm_first = !!size;
                sm.sm_height = height;

                error = recursive_scan(ip, NULL, &mp, 0, 0, 1, do_strip, &sm);
                if (error)
                        break;
        }

        gfs2_quota_unhold(ip);

out:
        gfs2_alloc_put(ip);
        return error;
}

static int trunc_end(struct gfs2_inode *ip)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct buffer_head *dibh;
        int error;

        error = gfs2_trans_begin(sdp, RES_DINODE, 0);
        if (error)
                return error;

        down_write(&ip->i_rw_mutex);

        error = gfs2_meta_inode_buffer(ip, &dibh);
        if (error)
                goto out;

        if (!ip->i_di.di_size) {
                ip->i_di.di_height = 0;
                ip->i_di.di_goal_meta =
                        ip->i_di.di_goal_data =
                        ip->i_num.no_addr;
                gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
        }
        ip->i_di.di_mtime = ip->i_di.di_ctime = get_seconds();
        ip->i_di.di_flags &= ~GFS2_DIF_TRUNC_IN_PROG;

        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
        gfs2_dinode_out(&ip->i_di, dibh->b_data);
        brelse(dibh);

out:
        up_write(&ip->i_rw_mutex);
        gfs2_trans_end(sdp);
        return error;
}

/**
 * do_shrink - make a file smaller
 * @ip: the inode
 * @size: the size to make the file
 * @truncator: function to truncate the last partial block
 *
 * Called with an exclusive lock on @ip.
 *
 * Returns: errno
 */

static int do_shrink(struct gfs2_inode *ip, u64 size)
{
        int error;

        error = trunc_start(ip, size);
        if (error < 0)
                return error;
        if (error > 0)
                return 0;

        error = trunc_dealloc(ip, size);
        if (!error)
                error = trunc_end(ip);

        return error;
}

/**
 * gfs2_truncatei - make a file a given size
 * @ip: the inode
 * @size: the size to make the file
 * @truncator: function to truncate the last partial block
 *
 * The file size can grow, shrink, or stay the same size.
 *
 * Returns: errno
 */

int gfs2_truncatei(struct gfs2_inode *ip, u64 size)
{
        int error;

        if (gfs2_assert_warn(GFS2_SB(&ip->i_inode), S_ISREG(ip->i_di.di_mode)))
                return -EINVAL;

        if (size > ip->i_di.di_size)
                error = do_grow(ip, size);
        else
                error = do_shrink(ip, size);

        return error;
}

int gfs2_truncatei_resume(struct gfs2_inode *ip)
{
        int error;
        error = trunc_dealloc(ip, ip->i_di.di_size);
        if (!error)
                error = trunc_end(ip);
        return error;
}

int gfs2_file_dealloc(struct gfs2_inode *ip)
{
        return trunc_dealloc(ip, 0);
}

/**
 * gfs2_write_calc_reserv - calculate number of blocks needed to write to a file
 * @ip: the file
 * @len: the number of bytes to be written to the file
 * @data_blocks: returns the number of data blocks required
 * @ind_blocks: returns the number of indirect blocks required
 *
 */

void gfs2_write_calc_reserv(struct gfs2_inode *ip, unsigned int len,
                            unsigned int *data_blocks, unsigned int *ind_blocks)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        unsigned int tmp;

        if (gfs2_is_dir(ip)) {
                *data_blocks = DIV_ROUND_UP(len, sdp->sd_jbsize) + 2;
                *ind_blocks = 3 * (sdp->sd_max_jheight - 1);
        } else {
                *data_blocks = (len >> sdp->sd_sb.sb_bsize_shift) + 3;
                *ind_blocks = 3 * (sdp->sd_max_height - 1);
        }

        for (tmp = *data_blocks; tmp > sdp->sd_diptrs;) {
                tmp = DIV_ROUND_UP(tmp, sdp->sd_inptrs);
                *ind_blocks += tmp;
        }
}

/**
 * gfs2_write_alloc_required - figure out if a write will require an allocation
 * @ip: the file being written to
 * @offset: the offset to write to
 * @len: the number of bytes being written
 * @alloc_required: set to 1 if an alloc is required, 0 otherwise
 *
 * Returns: errno
 */

int gfs2_write_alloc_required(struct gfs2_inode *ip, u64 offset,
                              unsigned int len, int *alloc_required)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        u64 lblock, lblock_stop, dblock;
        u32 extlen;
        int new = 0;
        int error = 0;

        *alloc_required = 0;

        if (!len)
                return 0;

        if (gfs2_is_stuffed(ip)) {
                if (offset + len >
                    sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode))
                        *alloc_required = 1;
                return 0;
        }

        if (gfs2_is_dir(ip)) {
                unsigned int bsize = sdp->sd_jbsize;
                lblock = offset;
                do_div(lblock, bsize);
                lblock_stop = offset + len + bsize - 1;
                do_div(lblock_stop, bsize);
        } else {
                unsigned int shift = sdp->sd_sb.sb_bsize_shift;
                lblock = offset >> shift;
                lblock_stop = (offset + len + sdp->sd_sb.sb_bsize - 1) >> shift;
        }

        for (; lblock < lblock_stop; lblock += extlen) {
                error = gfs2_extent_map(&ip->i_inode, lblock, &new, &dblock, &extlen);
                if (error)
                        return error;

                if (!dblock) {
                        *alloc_required = 1;
                        return 0;
                }
        }

        return 0;
}